Add ContactsChangeNotifier

[yonat]

• ** ContactsChangeNotifier**:
• https://github.com/yonat/ContactsChangeNotifier:
• Which contacts changed outside your app? Better CNContactStoreDidChange notification: Get real changes, without the noise.:
• Why it should be added to awesome-swift: Makes a difficult API easy, makes an objc-only API available from Swift.
• At least 15 stars (GitHub project)
• Support Swift 5
• Updated contents.json instead of README
• Lib is fully open sourced, written in Swift and not a wrapper over compiled lib
• Description does not say "written in Swift" or variant 🤓

[vpeschenkov]

@yonat thanks 👍